Particle flux shadowing for three-dimensional topography simulation

Abstract

In a three-dimensional (3-D) topography simulator, a method for removing sources of particle flux because of neighboring topology, for a point on a workpiece undergoing a deposition or etch process step. The method is practiced in a Generalized Solids Modeling system that utilizes a boundary representation model for representing a workpiece as one or more material object solids. For any given point on the 3-D structure, the neighboring topography forms a complex shadowing mask with respect to sources of particle flux, thus making analytical determination of visible sources of incoming particle flux difficult. The method is comprised generally of the steps of: defining a numerical mesh in a space over a surface of the workpiece; specifying an intensity of incident flux for each mesh point, identifying a set of mesh points defining a visible range of mesh points with respect to a particular target point and identifying mesh points in said set of mesh points that are obscured by neighboring topology.

We claim: 
     
       1. In a 3-D topography simulation system, a method for removing sources of particle flux that are obscured by neighboring topography with respect to a target point on a workpiece, said method comprising the steps of: a) providing a mesh in a space over said workpiece, said mesh having a plurality of mesh points corresponding to a point in said space;   b) specifying an intensity of incident particle flux for each mesh point in said mesh;   c) marking each of said mesh points as being visible to said target point;   d) marking mesh points that are not visible to said target point as being invisible to said target point;   e) marking mesh points that are obscured by neighboring topography as invisible to said target point; and   f) calculating movement of the target point based on the mesh points which are marked visible.   
     
     
       2. The method as recited in claim 1 wherein said step of marking mesh points that are not visible to said target point as being invisible to said target point, is further comprised of the steps of: a) constructing a point shadow polygon from the faces surrounding said target point;   b) projecting said point shadow polygon onto said mesh; and   c) marking mesh points that are not within said point shadow polygon as being invisible to said target point.   
     
     
       3. The method as recited in claim 2 wherein said step of marking mesh points that are obscured by neighboring topography as invisible is further comprised of the steps of: a) identifying a face corresponding to the neighboring topography facing said target point;   b) projecting said face onto said mesh; and   c) marking mesh points that are within said projected face as being invisible.   
     
     
       4. The method as recited in claim 3 wherein said mesh is a planar mesh. 
     
     
       5. The method as recited in claim 3 wherein said mesh is a spherical mesh. 
     
     
       6. In a topography simulation system for simulating the changes to the topography of a workpiece as materials are deposited and etched, a method for distinguishing sources of particle flux that do and do not contribute to a change to a target point on said workpiece during a manufacturing step, said method comprising the steps of: a) defining a plurality of sources of particle flux above said workpiece, each of said sources of particle flux having a particle flux intensity;   b) identifying one or more sources of particle flux as being visible to said target point;   c) marking said sources of particle flux identified in step b) as contributing to a change to said target point;   d) identifying a portion of said workpiece that is between said target point and one of said sources of particle flux that is visible to said target point; and   e) marking said sources of particle flux identified in step c) as contributing to a change to said target point.   
     
     
       7. The method as recited in claim 6 wherein said step of identifying one or more sources of particle flux that are visible to said target point is further comprised of the steps of: a) constructing a point shadow polygon towards said sources of particle incident flux for said target point based on adjacent topography;   b) projecting said point shadow polygon towards said sources of particle incident flux; and   c) identifying one or more sources of particle of flux that lie within a perimeter defined by said point shadow polygon.   
     
     
       8. The method as recited in claim 7 wherein said step of identifying a portion of said workpiece that is between said target point and one of said sources of particle flux that is visible to said target point is further comprised of the steps of: a) projecting a field of shadow corresponding to said portion of said workpiece; and   b) identifying one or more sources of particle flux that lie within a perimeter defined by said field of shadow that is also within said perimeter defined by said projected field of vision.